ventilation Misting/Fogging Windows

[Ethanthecarknownothing]

Hi all, with the colder weather we have been experiencing recently I've started to notice a rather annoying issue with my Fabia.

 

The front screen seems to be excessively misting and I'm trying to determine the cause.

 

Some days I'll get in the car with a clear screen start it and then the screen will begin misting around the windscreen air vent, almost as though the mist is coming from the ventilation system itself. I should point out that I can't see any mist though.

 

My thoughts are condensate pipe blockage, leak in the heater matrix or failing all of that a water leak somewhere I've not identified.

 

Using the air conditioning helps but it seems it randomly turns off and the screen suddenly fogs up when driving before starting to demist again.

 

Other probably completely unrelated things that could be worth a mention, I did notice a while ago some mist coming from the air conditioning on a hot day. I have recently had the air conditioning recharged and the air conditioning makes a slightly strange sound when used a wining and bubbling sound (similar to the sound some hotel air conditioning makes if you know that sound) that changes when you rev the car. 

 

I'm aware these problems all need fixing as well but unsure where to take it and mention them just in case they are connected.

 

Sorry for the all over the place post but trying to provide as much detail as possible.

 

If anyone has any ideas at all I'd really appreciate the advice.

 

Thanks in advance

 

Ethan

[Paws4Thot]

5 hours ago, Ethanthecarknownothing said:

The front screen seems to be excessively misting and I'm trying to determine the cause.

When was the cabin pollen filter last changed?

[Ethanthecarknownothing]

3 hours ago, Paws4Thot said:

When was the cabin pollen filter last changed?

This is a very good point and something I forgot to mention. I'm not sure when it was last changed and wanted to change it myself anyway. Do you know where it is located and how to gain access? Am I correct in saying it's on the passenger side somewhere behind the dash?

[Ootohere]

Do you have AC or Climate Control?

 

Do you use the AC when you can, which is if the ambient temp is above 2*oC.?

Has it ever been serviced?

 

Since you do not know if the pollen filter is clean / fresh what miles has the car done, and what model of Fabia is it?

 

Check the door seal drains at the bottom of the doors are cleaned out.

If the passenger door is not opened every day or regularly it might fill with water, not drain, it might even freeze in there.

 

Check your spare tyre well, see that there is no water in there. Check the spares tyre pressure while at it, and that you can get the wheels / bolts off if you have a puncture.

When were the back wheels last off if the car has drum brakes?

 

Maybe put a damp trap in the boot and in the car.

Edited 12 January by Rooted

[Jocko]

I found quite a pool of water in the spare wheel well of my Fabia. A judiciously drilled hole in one of the plugs solved that.

My pollen filter is accessible from the front passenger footwell, just below the dashboard.

[Ethanthecarknownothing]

10 hours ago, Rooted said:

Do you have AC or Climate Control?

 

Do you use the AC when you can, which is if the ambient temp is above 2*oC.?

Has it ever been serviced?

 

Since you do not know if the pollen filter is clean / fresh what miles has the car done, and what model of Fabia is it?

 

Check the door seal drains at the bottom of the doors are cleaned out.

If the passenger door is not opened every day or regularly it might fill with water, not drain, it might even freeze in there.

 

Thanks for the great advice, I've been using the AC pretty much constantly at the moment as it the only way I can see out! Recently when it's been icy obviously the compressor doesn't fire up but I dont get the misting either.

 

The car is a Fabia MK2 2009 or 5J and has done around 60,000 miles.

 

The AC was serviced a few months ago after it stopped blowing cold air.

 

I am going to replace the pollen filter tomorrow and keeping my fingers crossed it may help. I will also have a look at the door seal drains while I'm at it.

 

Thanks a lot!

[Ethanthecarknownothing]

7 hours ago, Jocko said:

I found quite a pool of water in the spare wheel well of my Fabia. A judiciously drilled hole in one of the plugs solved that.

My pollen filter is accessible from the front passenger footwell, just below the dashboard.

 

I have checked the spare (or where one would be as mine came without) and all is well there. 

 

Thanks for the info re the pollen filter.

[Ethanthecarknownothing]

I replaced the cabin filter today, 30 second job under the glovebox. Unfortunately no change there the fans do seem more powerful and there is perhaps a slight improvement.

 

Car unfortunately still very misty. It annoyingly causes my glasses to steam up while driving too!

 

I also checked the drains on the door seals both of which looked to be okay

 

I'm running out of ideas and at the moment the sudden misting can be quite dangerous. I'd appreciate any further ideas you guys may have, so far they've been great!

[Jocko]

Was the old cabin filter damp?

[sepulchrave]

What about the front scuttle drains?

[Ethanthecarknownothing]

1 hour ago, Jocko said:

Was the old cabin filter damp?

No it was completely dry but a little dirty. Not as bad as expected though and looked to have been changed recently. 

 

Will check the drains in a bit.

[Jocko]

Warm moist air is what causes the misting and that can only come from, as sepulchrave suggests, the scuttle drains, or the condensate drain. I suspect the latter as it is intermittent and could be caused by the switching (and thawing) of the air con.

[Ethanthecarknownothing]

11 minutes ago, Jocko said:

Warm moist air is what causes the misting and that can only come from, as sepulchrave suggests, the scuttle drains, or the condensate drain. I suspect the latter as it is intermittent and could be caused by the switching (and thawing) of the air con.

 

This is what I suspected. I'll see about getting under the car and shooting some compressed air in there.

 

Do you have any tips for locating the hose?

[Jocko]

My condensate comes down inside a box section on the driver's side. Check the open bottom is not clogged with muck.

[Breezy_Pete]

Engine bay side of firewall, hiding under the insulation, next to the heater matrix pipes.

Diagram shows  a LHD car, your drain will be on the other side of the pipes, I think. Look for a bump in the felt.

 

 

 

[Ethanthecarknownothing]

Thank you for all your responses, I have looked at both the scuttle and the AC drain. As far as I can tell, both are fine currently. It seems to only mist with the heat on in the car and for some reason seems to only really begin misting when moving.

[sepulchrave]

1 hour ago, Ethanthecarknownothing said:

Thank you for all your responses, I have looked at both the scuttle and the AC drain. As far as I can tell, both are fine currently. It seems to only mist with the heat on in the car and for some reason seems to only really begin misting when moving.

 

To be perfectly honest it sounds like your heater matrix may have sprung a leak, does it smell faintly of coolant inside the car? Have you checked the coolant level when the engine is cold?

[Ethanthecarknownothing]

46 minutes ago, sepulchrave said:

 

To be perfectly honest it sounds like your heater matrix may have sprung a leak, does it smell faintly of coolant inside the car? Have you checked the coolant level when the engine is cold?

 

Yes I did think it might be the case unfortunately. I think it could smell a little coolant but it doesn't seem to be going down massively.

 

Any idea where I could take it for this to be checked/fixed and the possible cost?

[Breezy_Pete]

Clean the screen with a white cloth or paper towel/tissue, and see if there's a colour match to what's in your expansion tank.

[sepulchrave]

11 minutes ago, Ethanthecarknownothing said:

 

Yes I did think it might be the case unfortunately. I think it could smell a little coolant but it doesn't seem to be going down massively.

 

Any idea where I could take it for this to be checked/fixed and the possible cost?

 

A tiny leak is sufficient to cause the misting you describe, a simple pressure test will reveal whether the system is leaking or not.

[Ethanthecarknownothing]

Excellent thanks for the advice I'll see if I can get my local garage to test the pressure.

[Ethanthecarknownothing]

Just had a look at my condensate drain as I do think this is likely a problem as well. I never notice any water under the car in the summer and I do notice mist occasionally from vent.

 

My photo shows what I could see, is this the drain itself or is that somewhere else.

 

How would I know if it is blocked?

[Breezy_Pete]

Yes that's the drain, more or less directly out of the bottom of the box the aircon evaporator lives in. Here's the view with whole thing out of car:

 

To see if it's blocked, run the A/C on a warm humid day and see if water comes out....

May have to wait a few months.

 

 

[Ethanthecarknownothing]

In a bizarre turn of events it would seem that I may have located the source of the problem. 

 

I was going to get my air compressor out the boot of the car today and noticed as Jocko previous mentiones it was sitting in a pool of water. Strange as previously it was bone dry...

 

I've managed to convince myself it was all sorts at this point causing it and now I'm starting to think I'm going mad!!

 

So my next steps are going to be identifying where the leak is coming from and then I'm probably going to get an air compressor on the condensate drain as well for good measure. Like I said I have noticed mist coming out of the vents in the summer so think this is likely an issue as well.

 

I'm slightly concerned about coolant smell but I think that could just be a bit of confirmation bias on my part there, at least I'm hoping!

 

Thank you all for your advice, looking forward to having a fog free car!

[sepulchrave]

The leak can really only be coming from the hatchback seal.